BRUSSELS — The killings of more than 130 U.S. and allied forces by Afghan troops or those dressed like them is not deterring NATO countries from the war in Afghanistan, two senior U.S. defense officials said Tuesday.

As NATO defense ministers gather this week, the top U.S. commander in Afghanistan will tell worried allies Wednesday what the U.S. is doing to stop the escalating insider attacks.

The officials told reporters that so far NATO ministers attending the conference here have not used the meeting to threaten any additional withdrawals of troops or to seek to limit the combat use of their forces as a result of the attacks.

U.S. officials, including Defense Secretary Leon Panetta, are expected to assure the ministers that commanders have come up with a range of ways to reduce the attacks. And they will insist that while the Taliban has seized on the attacks as a way to derail the fight and the trust between allied and Afghan forces, it is not yet a threat to the war strategy.

One of the officials said that NATO nations are concerned about both the safety of their forces and the impact on the war, so it is critical to have these discussions with the minister at this high level now. The officials said the coalition will stick to the withdrawal schedule, which has combat forces leaving and Afghan forces taking over security of the country by the end of 2014.

Both Marine Gen. John Allen, the top U.S. commander in Afghanistan, and U.S. Navy Adm. James Stravidis, NATO's top military commander, were at the alliance's gathering Tuesday along with Panetta, who was holding a series of individual meetings with other ministers. Panetta will make his formal address on Afghanistan to the ministers Wednesday.

The officials spoke on condition of anonymity because they were not authorized to speak publicly about the NATO strategy discussions.

Still, there are growing signs that the Afghan political and military hostilities are starting to wear on the coalition.

Compounding the insider attack threat is a recent spike in political tensions between Afghanistan's government leaders and the U.S.

Afghan President Hamid Karzai complained that the war effort is wrongheaded, and that coalition forces are not fighting the right enemy.

Just days ahead of the NATO meeting, Panetta was uncharacteristically sharp, criticizing Karzai for complaining rather than thanking the troops who have sacrificed their lives for his country. Karzai's argument that NATO is wrongly going after the Taliban in Afghanistan when it should be fighting insurgents in Pakistan's safe havens could further erode support for the war, particularly among members of Congress.

Panetta's pique reflects the frustration of his military commanders, who have seen more than 2,000 U.S. troops die in the 11-year war. And it can only fuel the grumbling by American lawmakers who are facing hotly contested elections next month, and are hearing from constituents wondering why the U.S. is pouring billions of dollars into a fight that Afghanistan's shaky and corruption-plagued government may no longer support.

One of the senior U.S. officials said that Karzai has made similar statements in the past, but noted they are still frustrated with Pakistan over the insurgent safe havens within its borders. Militants plan and wage attacks against coalition forces in Afghanistan, then retreat back across the border into Pakistan.

Support for the war has been ebbing across America and much of the world, triggering growing calls for a speedier troop withdrawal.

That prospect leaves commanders worried they won't have the forces they need to do the training and counterterrorism operations they believe necessary to continue the transition of security to the Afghan troops while also keeping the Taliban from resurging.

During meetings Tuesday, Rasmussen said the ministers are expected to endorse a new framework for the Afghan war after 2014, ending the combat focus and turning to a more expansive training and advisory role. As a result, NATO is working on a new name for the mission from the current International Security Assistance Force to something close to the International Training, Advisory and Assistance Mission in 2015.

That mission would also likely include continued counterterrorism efforts by the U.S.